Angiotensin II attenuates the natriuresis of water immersion in humans.

The hypothesis was tested that suppression of generation of ANG II is one of the mechanisms of the water immersion (WI)-induced natriuresis in humans. In one protocol, eight healthy young males were subjected to 3 h of 1) WI (WI + placebo), 2) WI combined with ANG II infusion of 0.5 ng · kg−1 · min−1 (WI + ANG II-low), and 3) a seated time control (Con). In another almost identical protocol, 7–10 healthy young males were investigated to delineate the tubular site(s) of action of ANG II by the lithium clearance method (CLi) and were on an additional fourth study day subjected to infusion of ANG II at a rate of 1.5 ng · kg−1 · min−1(WI + ANG II-high). During WI + placebo, plasma concentration of ANG II decreased from 16 ± 2 to 8 ± 1 pg/ml (P < 0.05) and renal sodium excretion increased from 104 ± 15 to 294 ± 27 μmol/min (P < 0.05). During WI + ANG II-low, plasma ANG II was not suppressed by WI, and the natriuresis was blunted by 52 ± 13% (P < 0.05). During WI + ANG II-low and WI + ANG II-high, an increase i...